tertiary ammonium cations having two partially double-bonded substitutions, RNH+R pyridinium, C5H5NH+ (protonated pyridine) quaternary ammonium cations having one double-bonded substitution and two single-bonded substitutions, iminium, (substituted protonated imine) diazenium, (substituted protonated diazene) thiazolium, (substituted protonated thiazole) quaternary ammonium cations having two double-bonded substitutions, R=N=R+ nitronium, bis(triphenylphosphine)iminium, ((C6H5)3P)2N+ quaternary ammonium cations having one triple-bonded substitution and one single-bonded substitution, R≡NR+ diazonium, N≡NR+ (substituted protonated nitrogen) nitrilium, RC≡NR+ (substituted protonated nitrile) tertiary oxonium cations having one triple-bonded substitution, R≡O+ acylium ions, R−C≡O+ ↔ R−C+=O nitrosonium, N≡O+ tertiary oxonium cations having two partially double-bonded substitutions, RO+R pyrylium, C5H5O+ tertiary sulfonium cations having one triple-bonded substitution, R≡S+ thionitrosyl, N≡S+ Double onium dications hydrazinediium or hydrazinium(2+) dication, +H3NNH (doubly protonated hydrazine) diazenediium cation, +H2N=NH (doubly protonated diazene) diazynediium cation, +HN≡NH+ (doubly protonated [di]nitrogen) Enium cations The extra bond is added to a less-common parent hydride, a carbene analog, typically named -ene or -ylene, which is neutral with 2 fewer bonds than the more-common hydride, typically named -ane or -ine. borenium cations, (protonated borylenes a.k.a. boranylidenes) carbenium cations, (protonated carbenes) have a trivalent carbon atom with a +1 charge. alkenium cations, (n ≥ 2) (protonated alkenes) methenium cation, (protonated methylene) ethenium, (protonated ethene) benzenium, (protonated benzene) tropylium, silylium cations, (protonated silylenes) nitrenium cations, (protonated nitrenes) phosphinidenium cations, (protonated phosphinidene) mercurinium cations, (protonated organomercury compounds; formed as intermediates in oxymercuration reactions) Substituted eniums diphenylcarbenium, (di-substituted methenium) triphenylcarbenium, (tri-substituted methenium) Ynium cations carbynium ions (protonated carbynes) have a divalent carbon atom with a +1 charge. alkynium cations, (n ≥ 2) (protonated alkynes) methynium cation, (protonated methylidyne radical) ethynium, (protonated ethyne) See also Carbonium ion Lyonium ion, a protonated solvent molecule Lyate ion, a deprotonated solvent molecule References External links Ions and Radicals, Queen Mary University of London Cations Chemical nomenclature